|Número de publicación||US5245616 A|
|Tipo de publicación||Concesión|
|Número de solicitud||US 07/888,456|
|Fecha de publicación||14 Sep 1993|
|Fecha de presentación||20 May 1992|
|Fecha de prioridad||24 Feb 1989|
|Número de publicación||07888456, 888456, US 5245616 A, US 5245616A, US-A-5245616, US5245616 A, US5245616A|
|Inventores||Gene H. Olson|
|Cesionario original||Rosemount Inc.|
|Exportar cita||BiBTeX, EndNote, RefMan|
|Citas de patentes (11), Otras citas (6), Citada por (169), Clasificaciones (18), Eventos legales (4)|
|Enlaces externos: USPTO, Cesión de USPTO, Espacenet|
This is a continuation of application Ser. No. 07/702,453 filed on May 16, 1991 abandoned as of the date of this application which is a continuation of application Ser. No. 07/315,395 filed Feb. 24, 1989 abandoned as of May 16, 1991.
1. Field of the Invention
This invention relates to a unit sending data packets to another unit through a communication medium or a link coupled between the units, and acknowledgement of data packets by the receiving unit.
2. Description of the Prior Art
Various techniques for acknowledging message packets in a communication system have been used, including ACK/NAK and sequencing protocols.
With the ACK/NAK protocol, a transmitting unit transmits a data packet to a receiving unit. If a receiving unit receives the packet, the receiving unit acknowledges receipt of the packet by transmitting back either an "ACK" acknowledgment signal indicating that the packet is correctly received, or a "NAK" no acknowledge signal indicating that the message is received, but not used. The NAK signal can indicate that there is an error in the received data or that the receiving unit is busy and cannot accept or use the data until a later time. If a NAK is received, the transmitting unit can automatically retransmit the data packet. The ACK or NAK signal is returned after each packet is sent, and before the next packet is sent. If the transmitting unit does not receive the expected ACK or NAK, from the receiving unit during an interval of time (called a time out interval) after transmission, the transmitting unit retransmits the same data packet. If an ACK signal is lost or garbled in transmission back to the transmitting unit, the transmitting unit will wait for the time out interval to elapse and then retransmit the data packet, even though the data packet was correctly received and used. If the communication medium is noisy or unreliable, time is wasted waiting for time outs and retransmitting data which has already been transmitted correctly, reducing the throughput of data, or performance for the communication system.
With the sequencing protocol, however, an acknowledgement is not necessarily sent after every packet; an acknowledgement may be sent after a group of packets is sent. The number of packets in the group can be selected based upon the reliability of the medium and transit or propagation time delays waiting for an acknowledgement to come back via the medium. When the medium conveys data reliably, the sequencing protocol can achieve higher data rates than the ACK/NAK protocol because less time is used by the receiver sending acknowledgements and by the transmitter waiting for acknowledgements.
With the sequencing protocol, counters in the transmitting and receiving units are synchronized at the start of the transmission of a group of packets. The transmitting unit's counter is incremented each time a packet is sent. The packet includes data indicating the count of the transmitting unit's counter. The receiving unit's counter is incremented only if a packet is received correctly and in proper sequence as indicated by the count. Thus, if one packet is not received correctly, all the following packets are ignored even if they are correctly received. After a packet, or a series of packets have been correctly received, the count of the receive counter is sent back to the transmitting unit as an acknowledgement signal to be compared to the count of the transmit counter. If no response is received by the transmitting unit after an interval of time (a time out interval), the transmitting unit begins retransmitting packets beginning with the first packet for which no acknowledgment was received. Then, all of the packets sent after that first lost packet must be retransmitted, even though many of them may have been accurately received already. The retransmission process is repeated until all of the packets in the group are received, as indicated when the transmit counter equals the last received receive counter.
In communication systems using a communication medium that is not near 100% reliable, both the ACK-NAK and the sequencing protocol suffer severe increases in the time required to send a series of message packets. With the ACK-NAK protocol, time is consumed by unnecessary time-outs and duplicate transmissions. With the sequencing protocol, time is consumed by unnecessary transmission of duplicate packets.
Thus a communication protocol is desired that transmits packets without waiting for an acknowledgment after each packet is sent from the receiving node and also with reduced transmission of unneeded duplicate message packets.
In the present invention, a transmitting unit sends a group of data packets to a receiving unit. The receiving unit responds by transmitting an acknowledgement output back to the transmitting unit, acknowledging whether the last received data packet and also a selected number of preceding packets sent to the receiving unit from the transmitting unit each have been received correctly. Responding to the acknowledgement, the transmitting unit selectively retransmits those data packets indicated to be not correctly received. A system comprises two or more of the units, also called nodes, linking together communication networks, such as in a process control system.
In such a system, an acknowledgement of a first packet sometimes fails to get back to the transmitting unit due to noise, a collision on the bus, or other causes, even though the first packet was received and used by the receiving unit. With the present invention, the transmitting unit transmits subsequent packets, without waiting a long "time out" interval, even though it failed to receive an acknowledgement of the first packet. After a subsequent data packet is transmitted, a subsequent acknowledgement signal is received back, and the subsequent acknowledgement signal contains data which replaces the lost acknowledgement of the first packet. The transmitting unit then responds in a way which makes good use of the time available on the bus. If the first packet was received correctly, it does not make a wasteful retransmission of the packet. If the first packet was not received correctly, or not received at all, the transmitting unit retransmits the lost packet. The transmitting unit can retransmit only the packet or packets which are lost. It does not need to retransmit a whole group of packets when only one packet is lost. Retransmission of data packets is thus selectively limitable to only those data packets which have been lost.
When each packet is sent, the data in each packet includes a word of redundant data calculated from the raw data desired to be transmitted. This redundant information usually takes the form of check digits or checksums. When each packet of data is received, the receiving unit calculates the redundant data independently and compares it to the transmitted redundant data to verify correct transmission. The receiving unit stores the result of this comparison, called "status", for each packet to be sent back as part of an acknowledgement.
Each node comprises a number of transmit counters. Each transmit counter is associated with a corresponding node in the system to which the transmitting node transmits packets. Each transmit counter in a transmitting unit generates a sequence number output which is incremented each time a packet is sent to the node associated with that counter. Each packet includes a layer of data indicating the sequence number or count of the counter. The receiving unit stores the sequence number associated with each data packet along with the status for that data packet in a memory or buffer. When a node sends back an acknowledgement, the acknowledgement includes data indicating the status for the last packet received, and also the status associated with a selected number of preceding sequence numbers. If a previously transmitted packet was not received, the status indicates that, as well. Multiple classes of status may be indicated for each packet. For example, three different classes of status for each packet may be, but is not limited to: received and accepted (ACK), received but not accepted (BUSY) or not received (NAK).
In a preferred embodiment, for example, the acknowledgement contains status information for the last eight packets. This is chosen based upon the user's evaluation of the characteristics of the transmission medium, such as reliability and propagation delay, and the user's tolerance for transmission errors. In this example, a transmitting node designated "node A" sends packets of data to a receiving node designated "node B". Node A comprises a modulo counter associated with the sequence number contained in messages transmitted to Node B which counts repetitively from 0 to 255. After each transmission of a packet from node A to node B, node B responds by transmitting back an acknowledgement to node A which includes the current counter number, the status of the last packet received from node A and the status of the seven packets with preceding counter numbers previously expected from node A. Thus unless eight consecutive acknowledgements from node B are lost, node A will always be informed of which packets in the transmitted sequence were received correctly by node B, which packets were received incorrectly or not received at all and which packets were received while node B was busy. Node A then renumbers those packets that were not properly received by node B and places them at the end of the sequence where they are retransmitted with new sequence numbers to node B. This process continues until the complete sequence is correctly received by node B. Additionally, at any time node A can interrogate node B concerning the status of the last eight messages received by node B.
It is also possible to piggyback or add this status information on packets being transmitted from node B to node A. Thus when there is a sequence of messages being exchanged both from node A to node B and also from node B to node A, status information concerning the most recently received packet along with the seven previously received packets is exchanged between the two nodes with very little overhead on the communication medium.
Using this new protocol, message packets are exchanged at increased speed while eliminating transmission of duplicate messages. Furthermore, the more unreliable the communication medium is in the communication system, the greater the benefits are of using this new communications protocol over the other communication protocols. The protocol is especially useful in a process control system which does not require that packets of information be received in a particular sequence or order. The protocol is also especially useful in a process control system in which it is desired to avoid the receiving of duplicates packets, such as packets including instructions to increment or decrement a counter.
FIG. 1 shows two nodes linking data between two process control systems in accordance with the present invention.
FIG. 2 shows data from a message packet and an acknowledgement transmitted on the communication system of FIG. 1.
FIG. 3 shows a section of the status field used in the message packet of FIG. 2.
FIG. 4 shows a section of the status field used in the message packet of FIG. 2.
FIG. 5 shows a portion of a communication system having nodes with multiple communication links.
In FIG. 1, a first process control system 11 comprises an operator console station, and controller stations coupled together by a communication bus 13 for sensing process parameters with sensors and controlling process parameters with process control devices. A second process control system 15, which can be similar to system 11, is interconnected with a second communication bus 17. The control systems 11 and 15 perform control functions on the same process, or on interrelated processes. Automatic transfer of packets of data or information between communication busses 11 and 15 and other systems is desired to improve control of the processes. Various forms of communication links such as coaxial cable 19, telephone modem link 21, and data bus 12, are available for transferring data packets between the busses 13 and 17 and the busses of other systems. The communication links, however, are sometimes less than completely reliable and an interface device is desired between the control system busses and the data links which automatically corrects errors which occur in transmission.
In FIG. 1, packets of data are transferred from bus 13 through an interface unit or node 14A, then along bus 12 to interface unit or node 14B, and finally to bus 17. Packets of data are transferred also from bus 17 through the interface unit 14B, then along bus 12 to interface unit 14A and finally to bus 13. Interface unit 14B is similar in design to interface device 14A, and the description below of the internal arrangement of interface device 14A with respect to control system 11 applies to interface device 14B with respect to control system 15, as well.
Interface unit 14A comprises a computer 18 performing calculation and control functions which couples data along a bus 28 internal to the interface unit 14A. The internal bus 28 can accommodate bi-directional data transfers. A transceiver 23 in interface unit 14A couples data packets back and forth between the control system bus 13 and the internal bus 28. A transceiver 20 in interface unit 14A couples data packets back and forth between the internal bus 28 and the data link 12. The transceiver 20 also couples data packets between the internal bus 28 and another similar interface unit 14C (shown in FIG. 5) along coaxial cable 19. The transceiver 20 in interface unit 14B, however, connects to a telephone modem link 21 rather than a coaxial cable link. The transceiver 20 in interface unit 14A includes a transmitter 20A for transmitting data packets to links 12 and 19 and a receiver 20B for receiving data packets from links 12 and 19. A memory 26 connects to computer 18 through bus 28. Memory 26 includes a portion for receive counters 30, transmit counters 32 and status words 34. Computer 18 controls transfer of data internal to the interface unit 14A to accomplish transfer of packets between busses 12 and 13, and performs acknowledgement and message correction functions according to the invention.
The message packets transmitted over links 12, 19, 21 can take a variety of forms. Various known methods of modulation, layering of control words, preambles, delimiters, serial or parallel formats, and the like, can be implemented into the message packets to make them compatible with the type of link or physical layer of communication which has been selected for use. Two message packets are shown schematically in FIG. 2. Packet 36A represents a packet sent from interface unit 14A to interface unit 14B in FIG. 1. Packet 36B represents packets sent from interface unit 36B to interface unit 14A in FIG. 1. Packets 36A and 36B have a number of different fields, including protocol sections 38A and 38B followed by message data fields 40A and 40B, respectively. Protocol section 38A and 38B include bit count fields 42A and 42B indicating the total number of bits in packets 36A and 36B, respectively. Protocol sections 38A and 38B also comprise transmit sequence fields 44A and 44B indicating the sequence of the data in message data fields 40A and 40B (e.g. 0-255), respectively, receive sequence fields 46A and 46B indicating the sequence number of the last message received (e.g. 0-255), status inquiry bits 48A and 48B, acknowledgment (ACK) fields 50A and 50B and BUSY fields 52A and 52B, respectively. Message packets 36A and 36B also include a field of redundant data 54A and 54B, respectively, such as a check sum calculated by the sending unit from message data 40A or 40B. Message data 40A or 40B is usually a large number of bytes, for example, 128 bytes and can include additional redundant data such as check digits.
After packet 36A is sent by interface unit 14A to interface unit 14B, packet 36B shown in FIG. 2 is sent back as an acknowledgement. Packet 36B includes bit count field 42B indicating the length of the message data 40B. Packet 36B includes receive sequence field 46B indicating the sequential message number of the packet being acknowledged. ACK field 50B and BUSY field 52B indicate respectively whether each of the last 8 packets have been received and whether the interface unit 14B was busy when the packet was received. Fields 50B, 52B together indicate status of packets previously sent to interface unit 14A on link 12 in FIG. 1.
FIG. 3 shows a detailed view of ACK field 50B. Acknowledgment field 50B comprises acknowledgment bits 50B0 through 50B7 indicating whether each of the last eight packets has been received. BUSY field 52B shown in FIG. 4 comprises busy bits 52B0 through 52B7 indicating whether interface unit 14B was busy when each of the last eight packets of data was received.
In operation, nodes 14A and 14B shown in FIG. 1 are in communication with each other using communication link 12. Message packets such as 36A and 36B are transmitted on communication link 12 bi-directionally between node 14A and node 14B. A protocol section, 38A or 38B, for example, acknowledging a first packet of data going in a first direction on link 12 can include data in the data field, 40A or 40B, going back in an opposite direction on link 12 to the unit which transmitted the first packet of data. For example, assume node 14A is transmitting a sequence of message packets similar to packet 36A to node 14B. The message number in the transmit sequence field 44A in protocol section 38A of each message packet 36A sent from node 14A to node 14B will contain that message packet's sequential message number. These message numbers may be in the range from zero to 255. The sequence repeats once the message number in the transmit sequence field 44 reaches 255. Referring to FIG. 1, node 14A receives input data on the input data bus 13. This input data is passed and moved to the message data field 40A by computer 18. Computer 18 forms the message packet 36A by adding protocol section 38A to message data field 40A. The computer 18 in node 14A also adds acknowledgements for other packets to the ACK field 50A and BUSY field 52A in protocol section 36A. The message number in transmit sequence field 44A in protocol section 38A is recalled from transmit counters 32 of memory array 26 in node 14A. The receive number in receive sequence field 46A in protocol section 38A is recalled from receive counters 30 of memory array 26 in node 14A. Computer 18 of node 14A recalls information for acknowledgment field 50A and BUSY field 52A from the memory 34 as explained below. Status inquiry bit 48A is added by computer 18 as explained below. After forming message packet 36A, computer 18 passes message packet 36A to transceiver 20 along internal bus 28. Transceiver 20 formats this message packet for transmission along communication link 12.
As node 14A sends a sequence of message packets 36A, they are received at node 14B. In response to each message packet 36A received from node 14A, node 14B forms a packet 36B for transmission back to node 14A. For example, after a message is received by node 14B from node 14A, node 14B would transmit a packet 36B having message number fields corresponding to those in the packets being acknowledged.
Referring to FIG. 3, the individual bits 50B0-50B7 that comprise the data in ACK field 50B are shown. For example, the "1" in ACK bit 50B0 indicates that the last message from node 14A was properly received. The "0" in acknowledgment bit 50B1 indicates that the second to the last message received by node 14B from node 14A either not received or improperly received as indicated by comparing the checksum data in 54A with the checksum as calculated by node 14B. This code continues for acknowledgment bits 50B2 through 50B7. Thus each acknowledgment bit 50B0 through 50B7 represents an offset message number such that the actual message number is referenced from a base value stored in receive sequence field 46B indicating the message number of the last message received by node 14B from node 14A. For example when receive sequence field 46B contains "22", acknowledgment bit 50B0 represents message "22", acknowledgment bit 50B1 represents message "21", acknowledgment bit 50B2 represents message "20", and so forth.
The BUSY field 52B carries the busy status of the last eight messages received by node 14B from node 14A. For example, when the busy field 52 for node B contains the number "16" (binary 0001 0000), busy bit 52B3 shown in FIG. 4 carries a "1" while busy bits 52B0-52B2 and 52B3-52B7 carry "0". This indicates that node 14B was busy when the fourth to the last message was received. This may have occurred because the buffers at node 14B were full or because node 14B was for some other reason unable to accept the message. Similar to ACK field 50B, each busy bit 52B0 through 52B7 in the BUSY field 52 represents an offset value from a base message value contained in receive sequence field 46B. For example, when receive sequence field 46B carries the number "22", busy bit 52B0 represents the busy status of message number "22" received by node 14B from node 14A, busy bit 52B1 corresponds to message "21", busy bit 52B2 corresponds to message "20 ", and so forth.
When node 14A receives packet 36B, node 14A will calculate that messages "19" through "21" were not acknowledged and when message "19" was received by node 14B, node 14B was busy. Node 14A would then place messages "19" through "21" on the top of the stack of messages in line for transmission to node 14B. Messages "19" through "21" would be correspondingly renumbered in the sequence prior to transmission to node 14B.
In severe conditions, eight consecutive messages could be lost in transmission from node 14A to node 14B while node 14B had either not transmitted any message packets 36B to node 14A or those message packets had also been lost in transmission. In this situation, node 14A can send a message packet with status inquiry bit (SIB) in field 48A of protocol section 38A set to "1". When node 14B receives message packet 36A with SIB 48A set to "1", if that packet 36A contains no data in message data field 40A as indicated by the contents of bit count field 42A node 14B responds immediately with a message packet 36B including its current protocol section 38B without updating the receive number stored in memory 30 of node 14B. Node 14A continues transmitting message packets 36A with status inquiry bit in data field 48A set to "1" until node 14A receives a response from node 14B. Thus the system will default to a time-out type protocol only after eight consecutive message packets 36A are lost in transmission to node 14B.
FIG. 5 shows a diagram of a complex communication network 60 having numerous nodes 14A through 14H interconnected by links 12, 19, 21, and 61-73. The nodes in the network have can pass packets between their associated process control systems (not shown) and the connected links, and further from one connected link to another connected link so that messages can be passed from node to node. Such communication networks often have a number of different "levels" responsible for transporting the message from node to node. For example, the communication network may have a high level concerned only with overall network configuration and addressing. There may be an intermediary level or transport level concerned with intermediary communication functions such as the path a message is intended to follow between two nodes. For example, arrows in FIG. 5 indicate one possible path for message packets between nodes 14A and 14H. Finally there may be a low level or link level concerned only with transmitting a message over a single communication link such as link 12. Thus, it is the link level that carries out the functions associated with transmitting a message between node 14A and node 14B, node 14B and 14D, node 14D and 14E, and node 14E and 14H using the path indicated by the arrows between nodes 14A and 14H in FIG. 5.
Assuming each communication link such as links 12, 19, 21, and 61-73 shown in FIG. 5 has a 70% reliability, each communication link in the path between 14A and 14H individually lowers the probability that the message reaches the destination node. For example, using communication links with 70% reliability, the probability of the message reaching node 14H from node 14A along the path indicated by the arrows is 0.74 =0.24 or 24%. After receiving the message from node 14A, node 14H must in some way acknowledge the message. Node 14H's acknowledgment also only has a 24% probability of reaching node 14A following the reverse path indicated by the arrows in FIG. 6. Thus the overall probability of node 14A transmitting a message to node 14H and properly receiving node 14H's response is 0.78 =0.058 or 5.8%.
In a communication system such as shown in FIG. 5, the improved technique for acknowledging packets of the present invention is well suited for implementation on the link level. The link level thus assures substantially 100% probability that the message is received between two adjacent nodes such that the transport level and the high level may be configured as if the link level is substantially 100% reliable.
For each node with which a node in a communication system will be exchanging message packets such as 36A or 36B, separate receive counters 30, transmit counters 32 and status information for previously received messages must be stored in the memory array 26 shown in node 14A of FIG. 1. For example, in the communication system FIG. 5 each node 14A, 14B, 14C, etc. would exchange message packets like 36A and 36B with only the directly connected nodes if the protocol of the present invention were implemented on the link level. Thus node 14D, 14G in system 60 of FIG. 5 would each require four receive counters 30 and four transmit counters 32. Each node 14A, 14B, 14C, etc. would also be required to store the status of the eight previously received messages from each of the four adjacent nodes 14 in the memory 34 of memory array 26. Using additional computer memory and packets which contain address fields, the present invention may be implemented at a higher communication level such as the intermediary level.
This technique for acknowledging message packets ensures high speed communication between nodes in a communication system even when the communication links 12 in the system offer poor reliability. The technique reduces the number of duplicate message transmissions and decreases the amount of time spent waiting for time outs to occur.
Although the present invention is described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, although a system and method is described in which only three types of status for the eight previous messages is maintained, other numbers of messages could be used or protocol sections having more than three status types could be included in the message packets.
|Patente citada||Fecha de presentación||Fecha de publicación||Solicitante||Título|
|US4422171 *||29 Dic 1980||20 Dic 1983||Allied Corporation, Law Department||Method and system for data communication|
|US4439859 *||10 Ago 1981||27 Mar 1984||International Business Machines Corp.||Method and system for retransmitting incorrectly received numbered frames in a data transmission system|
|US4617657 *||31 Dic 1984||14 Oct 1986||Northern Telecom Limited||Transmitting sequence numbers of information in a packet data transmission system|
|US4797881 *||12 Mar 1987||10 Ene 1989||Sytek, Inc.||Bridge system for connecting networks|
|US4805169 *||7 Feb 1986||14 Feb 1989||Hollandse Signaalapparaten B.V.||Local area network operating on the multiple bus system|
|US4841526 *||19 Nov 1986||20 Jun 1989||Wilson Jon C||Data communications system|
|EP0162478A2 *||24 May 1985||27 Nov 1985||Ntx Communications Corporation||Method and apparatus for high speed satellite communication|
|EP0186343A2 *||3 Dic 1985||2 Jul 1986||Northern Telecom Limited||Transmitting sequence numbers of information in a packet data transmission system|
|EP0229353A2 *||18 Dic 1986||22 Jul 1987||International Business Machines Corporation||Method and system for handling transmission errors|
|GB2180127A *||Título no disponible|
|GB2206020A *||Título no disponible|
|1||"Deadlock Avoidance In Store and Forward Networks--I: Store and Forward Deadlock", Philip M. Merlin and Paul J. Schweitzer, IEEE Transactions on Communications, vol. Com-28, No. 3, Mar. 1980, pp. 345-353.|
|2||Brodd, W., "HDLC ADCCP, and SDLC: What's the Difference?", Data Communications, Aug. 1983.|
|3||*||Brodd, W., HDLC ADCCP, and SDLC: What s the Difference , Data Communications, Aug. 1983.|
|4||*||Deadlock Avoidance In Store and Forward Networks I: Store and Forward Deadlock , Philip M. Merlin and Paul J. Schweitzer, IEEE Transactions on Communications, vol. Com 28, No. 3, Mar. 1980, pp. 345 353.|
|5||*||Tanenbaum, A., Computer Networks, 2nd ed., Prentice Hall, 1988, pp. 212 239.|
|6||Tanenbaum, A., Computer Networks, 2nd ed., Prentice-Hall, 1988, pp. 212-239.|
|Patente citante||Fecha de presentación||Fecha de publicación||Solicitante||Título|
|US5371731 *||9 Oct 1991||6 Dic 1994||British Telecommunications Public Limited Company||Network traffic management|
|US5386412 *||11 May 1993||31 Ene 1995||Park; Jung S.||Telecommunication system protocol for asynchronous data communication between multiport switch control processor and information support personal computer terminal|
|US5440545 *||2 Ago 1993||8 Ago 1995||Motorola, Inc.||Packet delivery system|
|US5444718 *||30 Nov 1993||22 Ago 1995||At&T Corp.||Retransmission protocol for wireless communications|
|US5450578 *||23 Dic 1993||12 Sep 1995||Unisys Corporation||Method and apparatus for automatically routing around faults within an interconnect system|
|US5530909 *||25 Mar 1994||25 Jun 1996||Sextant Avionique||Method for Radio transmitting information using aircrafts as open transmission relays|
|US5553075 *||22 Jun 1994||3 Sep 1996||Ericsson Ge Mobile Communications Inc.||Packet data protocol for wireless communication|
|US5555266 *||4 Oct 1993||10 Sep 1996||Motorola, Inc.||Method for reducing transmission delays in a packet transmission system|
|US5590366 *||13 Abr 1995||31 Dic 1996||Digital Equipment Corporation||Packet forwarding system for measuring the age of data packets flowing through a computer network|
|US5617561 *||22 Dic 1994||1 Abr 1997||International Business Machines Corporation||Message sequence number control in a virtual time system|
|US5701305 *||3 Mar 1995||23 Dic 1997||Hewlett-Packard Company||Error recovery in a network having cascaded hubs|
|US5745685 *||29 Dic 1995||28 Abr 1998||Mci Communications Corporation||Protocol extension in NSPP using an acknowledgment bit|
|US5748100 *||6 Oct 1995||5 May 1998||Motorola, Inc.||Reliable wireless message distribution system|
|US5751719 *||30 Nov 1995||12 May 1998||Lucent Technologies Inc.||Method and system for data transfer in the presence of disconnects|
|US5768250 *||20 May 1997||16 Jun 1998||Hewlett-Packard Company||Error recovery in a network having cascaded hubs|
|US5815667 *||28 Nov 1995||29 Sep 1998||Ncr Corporation||Circuits and methods for intelligent acknowledgement based flow control in a processing system network|
|US5844478 *||13 Ago 1996||1 Dic 1998||Thomson Consumer Electronics, Inc.||Program specific information formation for digital data processing|
|US5872777 *||30 Sep 1997||16 Feb 1999||Motorola, Inc.||Method and apparatus for conveying data packets in a packet data communication system|
|US5894547 *||17 May 1994||13 Abr 1999||International Business Machines Corporation||Virtual route synchronization|
|US5974028 *||24 Feb 1997||26 Oct 1999||At&T Corp.||System and method for improving transport protocol performance in communication networks having lossy links|
|US6032180 *||31 Mar 1997||29 Feb 2000||Fujitsu Limited||Image data transmission system, video server unit, and client unit for displaying image data|
|US6038606 *||25 Nov 1997||14 Mar 2000||International Business Machines Corp.||Method and apparatus for scheduling packet acknowledgements|
|US6049570 *||9 Dic 1997||11 Abr 2000||Oki Electric Industry Co., Ltd.||Picture coder|
|US6104712 *||22 Feb 1999||15 Ago 2000||Robert; Bruno G.||Wireless communication network including plural migratory access nodes|
|US6108809 *||6 Nov 1995||22 Ago 2000||Siemens Aktiengesellschaft||Method for sending messages from a lower-level controller to a higher-level controller|
|US6128283 *||3 Dic 1997||3 Oct 2000||Nortel Networks Corporation||Method and apparatus for data transmission using a positive group acknowledgement protocol|
|US6161207 *||15 Nov 1996||12 Dic 2000||Motorola, Inc.||Communications unit and method of communicating having efficient packet acknowledgement|
|US6163540 *||17 Mar 1998||19 Dic 2000||Lsi Logic Corporation||System and method for establishing unique sequence identification in an information exchange of a system network|
|US6208620 *||2 Ago 1999||27 Mar 2001||Nortel Networks Corporation||TCP-aware agent sublayer (TAS) for robust TCP over wireless|
|US6367045 *||1 Jul 1999||2 Abr 2002||Telefonaktiebolaget Lm Ericsson (Publ)||Bandwidth efficient acknowledgment/negative acknowledgment in a communication system using automatic repeat request (ARQ)|
|US6470391 *||8 May 2001||22 Oct 2002||Hitachi, Ltd.||Method for transmitting data via a network in a form of divided sub-packets|
|US6526049 *||18 Dic 1996||25 Feb 2003||Mitsubishi Denki Kabushiki Kaisha||Packet transferring device|
|US6564071 *||26 Jun 1998||13 May 2003||Microcom Systems, Inc.||Transmission of data over a radio frequency channel|
|US6603389 *||18 Oct 1999||5 Ago 2003||Motorola, Inc.||Method for indicating a delinquent response to a message from a selective call device|
|US6629261||21 Nov 2000||30 Sep 2003||At&T Wireless Services, Inc.||Enhanced data link layer selective reject mechanism in noisy wireless environment|
|US6631479 *||10 Abr 2000||7 Oct 2003||Rohm Co., Ltd||Data processing system, data processor and data processing method|
|US6662213 *||10 Ene 2000||9 Dic 2003||Sun Microsystems, Inc.||System and method for ensuring delivery of a single communication between nodes|
|US6693880 *||20 Jun 2001||17 Feb 2004||International Business Machines Corporation||System of controlling the flow of information between senders and receivers across links being used as channels|
|US6701198 *||21 Sep 2000||2 Mar 2004||Rockwell Automation Technologies, Inc.||Safety network for industrial controller allowing initialization on standard networks|
|US6711128 *||15 Dic 1998||23 Mar 2004||At&T Corp.||System and method for improving transport protocol performance in communication networks having lossy links|
|US6728237||11 Mar 1999||27 Abr 2004||Telefonaktiebolaget Lm Ericsson (Publ)||Arrangement, a system and a method relating to a packet data communication|
|US6731648 *||16 Sep 1998||4 May 2004||British Telecommunications Plc||Method and apparatus for transmitting a return signal in a loop network|
|US6781986||25 Jun 1999||24 Ago 2004||Nortel Networks Limited||Scalable high capacity switch architecture method, apparatus and system|
|US6898751||31 Jul 2002||24 May 2005||Transdimension, Inc.||Method and system for optimizing polling in systems using negative acknowledgement protocols|
|US6915444 *||12 Sep 2001||5 Jul 2005||Rockwell Automation Technologies, Inc.||Network independent safety protocol for industrial controller using data manipulation techniques|
|US6941501 *||10 Ago 2001||6 Sep 2005||Kddi Corporation||Multicast file transmission method|
|US6970476||26 Sep 2000||29 Nov 2005||Telefonaktiebolaget Lm Ericsson (Publ)||Efficient header compression context update in packet communications|
|US7009951 *||9 Feb 2001||7 Mar 2006||Nokia Mobile Phones, Ltd.||Data packet numbering in mobile packet switched data transmission|
|US7009957 *||28 Feb 2002||7 Mar 2006||Airmagnet, Inc.||Measuring the throughput of transmissions over wireless local area networks|
|US7009967 *||4 Ago 2000||7 Mar 2006||Shrikumar Hariharasubrahmanian||Systems and methods for transmitting data packets|
|US7085869 *||4 Abr 2001||1 Ago 2006||Advanced Micro Devices, Inc.||Arrangement for managing transmitted packets requiring acknowledgement in a host channel adapter|
|US7107358||12 Sep 2001||12 Sep 2006||Rockwell Automation Technologies, Inc.||Bridge for an industrial control system using data manipulation techniques|
|US7167448||4 Feb 2002||23 Ene 2007||Sun Microsystems, Inc.||Prioritization of remote services messages within a low bandwidth environment|
|US7167475 *||9 Feb 2001||23 Ene 2007||Nokia Corporation||Data packet numbering in packet-switched data transmission|
|US7181455||27 Jun 2002||20 Feb 2007||Sun Microsystems, Inc.||Bandwidth management for remote services system|
|US7240109||27 Jun 2002||3 Jul 2007||Sun Microsystems, Inc.||Remote services system service module interface|
|US7260623||27 Jun 2002||21 Ago 2007||Sun Microsystems, Inc.||Remote services system communication module|
|US7298693||20 Oct 2000||20 Nov 2007||Tellabs Operations, Inc.||Reverse notification tree for data networks|
|US7305486||28 Jun 2001||4 Dic 2007||Kanad Ghose||System and method for fast, reliable byte stream transport|
|US7308617||17 Jun 2004||11 Dic 2007||International Business Machines Corporation||Apparatus, system, and method for automatically freeing a server resource locked awaiting a failed acknowledgement from a client|
|US7315510 *||20 Oct 2000||1 Ene 2008||Tellabs Operations, Inc.||Method and apparatus for detecting MPLS network failures|
|US7327735||27 Nov 2002||5 Feb 2008||Alcatel Canada Inc.||System and method for detecting lost messages transmitted between modules in a communication device|
|US7406537 *||6 Feb 2004||29 Jul 2008||Progress Software Corporation||Dynamic subscription and message routing on a topic between publishing nodes and subscribing nodes|
|US7417948 *||13 Jul 2001||26 Ago 2008||Nokia Corporation||Controlled data network error recovery|
|US7505412 *||22 Dic 2003||17 Mar 2009||Ntt Docomo, Inc.||Transmission control method and system|
|US7603606||3 Jul 2000||13 Oct 2009||Nokia Corporation||Method and system for data reception acknowledgement|
|US7620728 *||4 Feb 2004||17 Nov 2009||Nxp B.V.||Method of monitoring the communication in a network|
|US7653091||30 Jun 2005||26 Ene 2010||Radioshack Corporation||Apparatus for synchronization of digital multimedia data communicated over wired media|
|US7721004||3 Ago 2006||18 May 2010||Rockwell Automation Technologies, Inc.||Bridge for an industrial control system using data manipulation techniques|
|US7796504||20 Oct 2000||14 Sep 2010||Tellabs Operations, Inc.||Method for establishing an MPLS data network protection pathway|
|US7849376 *||29 Sep 2009||7 Dic 2010||Nokia Corporation||Data acknowledgement|
|US7881184||14 Ago 2007||1 Feb 2011||Tellabs Operations, Inc.||Reverse notification tree for data networks|
|US7899925||4 Dic 2007||1 Mar 2011||Kanad Ghose||System and method for fast, reliable byte stream transport|
|US7940706||10 May 2011||International Business Machines Corporation||Controlling the state of duplexing of coupling facility structures|
|US8031593 *||2 Jul 2008||4 Oct 2011||Nokia Corporation||Controlled data network error recovery|
|US8130637||21 Dic 2007||6 Mar 2012||Tellabs Operations, Inc.||Method and apparatus for detecting MPLS network failures|
|US8140928 *||15 Jun 2007||20 Mar 2012||Ntt Docomo, Inc.||Radio communications apparatus and method used in a mobile communications system|
|US8191078||22 Mar 2005||29 May 2012||Progress Software Corporation||Fault-tolerant messaging system and methods|
|US8266239||27 Jun 2002||11 Sep 2012||Oracle International Corporation||Remote services system relocatable mid level manager|
|US8276115||4 Feb 2008||25 Sep 2012||Progress Software Corporation||Automated construction and deployment of complex event processing applications and business activity monitoring dashboards|
|US8281108||20 Ene 2003||2 Oct 2012||Martin Vorbach||Reconfigurable general purpose processor having time restricted configurations|
|US8281265||19 Nov 2009||2 Oct 2012||Martin Vorbach||Method and device for processing data|
|US8301720||18 Jul 2006||30 Oct 2012||Progress Software Corporation||Method and system to collect and communicate problem context in XML-based distributed applications|
|US8301800||1 Jul 2003||30 Oct 2012||Actional Corporation||Message processing for distributed computing environments|
|US8301872||4 May 2005||30 Oct 2012||Martin Vorbach||Pipeline configuration protocol and configuration unit communication|
|US8310274||4 Mar 2011||13 Nov 2012||Martin Vorbach||Reconfigurable sequencer structure|
|US8312200||21 Jul 2010||13 Nov 2012||Martin Vorbach||Processor chip including a plurality of cache elements connected to a plurality of processor cores|
|US8312301||30 Sep 2009||13 Nov 2012||Martin Vorbach||Methods and devices for treating and processing data|
|US8341188||13 Abr 2011||25 Dic 2012||International Business Machines Corporation||Controlling the state of duplexing of coupling facility structures|
|US8407525||24 Oct 2011||26 Mar 2013||Pact Xpp Technologies Ag||Method for debugging reconfigurable architectures|
|US8429385||19 Sep 2002||23 Abr 2013||Martin Vorbach||Device including a field having function cells and information providing cells controlled by the function cells|
|US8468329||8 Jun 2012||18 Jun 2013||Martin Vorbach||Pipeline configuration protocol and configuration unit communication|
|US8471593||4 Nov 2011||25 Jun 2013||Martin Vorbach||Logic cell array and bus system|
|US8503451 *||8 May 2007||6 Ago 2013||Broadcom Corporation||Limited automatic repeat request protocol for frame-based communication channels|
|US8516054||14 Nov 2001||20 Ago 2013||Aurea Software, Inc.||Message handling|
|US8588058||15 Dic 2010||19 Nov 2013||Tellabs Operations, Inc.||Reverse notification tree for data networks|
|US8656350||4 Feb 2008||18 Feb 2014||Software Ag||Event-based process configuration|
|US8686475||9 Feb 2011||1 Abr 2014||Pact Xpp Technologies Ag||Reconfigurable elements|
|US8686549||30 Sep 2009||1 Abr 2014||Martin Vorbach||Reconfigurable elements|
|US8700070||7 Nov 2007||15 Abr 2014||Motorola Mobility Llc||System and method for adaptive message retransmission|
|US8726250||10 Mar 2010||13 May 2014||Pact Xpp Technologies Ag||Configurable logic integrated circuit having a multidimensional structure of configurable elements|
|US8737203||5 Ago 2010||27 May 2014||Tellabs Operations, Inc.||Method for establishing an MPLS data network protection pathway|
|US8803552||25 Sep 2012||12 Ago 2014||Pact Xpp Technologies Ag||Reconfigurable sequencer structure|
|US8819505||30 Jun 2009||26 Ago 2014||Pact Xpp Technologies Ag||Data processor having disabled cores|
|US8832580||5 Nov 2009||9 Sep 2014||Aurea Software, Inc.||Software with improved view of a business process|
|US8842516||6 Ago 2010||23 Sep 2014||Tellabs Operations, Inc.||Protection/restoration of MPLS networks|
|US8842528||2 Oct 2012||23 Sep 2014||At&T Intellectual Property Ii, Lp||System and method for improving transport protocol performance in communication networks having lossy links|
|US8869121||7 Jul 2011||21 Oct 2014||Pact Xpp Technologies Ag||Method for the translation of programs for reconfigurable architectures|
|US8914590||30 Sep 2009||16 Dic 2014||Pact Xpp Technologies Ag||Data processing method and device|
|US9009234||5 Feb 2008||14 Abr 2015||Software Ag||Complex event processing system having multiple redundant event processing engines|
|US9047440||28 May 2013||2 Jun 2015||Pact Xpp Technologies Ag||Logical cell array and bus system|
|US9075605||17 Oct 2012||7 Jul 2015||Pact Xpp Technologies Ag||Methods and devices for treating and processing data|
|US9081743 *||25 May 2012||14 Jul 2015||Pro Design Electronic Gmbh||Communication system and communicaton method|
|US9178661||30 Sep 2011||3 Nov 2015||Microsoft Technology Licensing, Llc||Controlled data network error recovery|
|US20010017850 *||9 Feb 2001||30 Ago 2001||Nokia Mobile Phones Ltd.||Data packet numbering in packet-switched data transmission|
|US20010030965 *||9 Feb 2001||18 Oct 2001||Nokia Mobile Phones Ltd.||Data packet numbering in packet-switched data transmission|
|US20020009053 *||13 Jul 2001||24 Ene 2002||Kai Sjoblom||Controlled data network error recovery|
|US20020038441 *||10 Ago 2001||28 Mar 2002||Kazuyuki Eguchi||Multicast file transmission method|
|US20030051053 *||12 Sep 2001||13 Mar 2003||Vasko David A.||Bridge for an industrial control system using data manipulation techniques|
|US20030051203 *||12 Sep 2001||13 Mar 2003||Vasko David A.||Network independent safety protocol for industrial controller using data manipulation techniques|
|US20030135575 *||27 Jun 2002||17 Jul 2003||Richard Marejka||Self-monitoring and trending service system with cascaded pipeline linking numerous client systems|
|US20030147350 *||4 Feb 2002||7 Ago 2003||Wookey Michael J.||Prioritization of remote services messages within a low bandwidth environment|
|US20030149740 *||4 Feb 2002||7 Ago 2003||Wookey Michael J.||Remote services delivery architecture|
|US20030149771 *||4 Feb 2002||7 Ago 2003||Wookey Michael J.||Remote services system back-channel multicasting|
|US20030149889 *||4 Feb 2002||7 Ago 2003||Wookey Michael J.||Automatic communication and security reconfiguration for remote services|
|US20030161341 *||28 Feb 2002||28 Ago 2003||Miles Wu||Measuring the throughput of transmissions over wireless local area networks|
|US20030163544 *||4 Feb 2002||28 Ago 2003||Wookey Michael J.||Remote service systems management interface|
|US20030177259 *||4 Feb 2002||18 Sep 2003||Wookey Michael J.||Remote services systems data delivery mechanism|
|US20030212738 *||10 May 2002||13 Nov 2003||Wookey Michael J.||Remote services system message system to support redundancy of data flow|
|US20040001514 *||27 Jun 2002||1 Ene 2004||Wookey Michael J.||Remote services system communication module|
|US20040002978 *||27 Jun 2002||1 Ene 2004||Wookey Michael J.||Bandwidth management for remote services system|
|US20040003083 *||27 Jun 2002||1 Ene 2004||Wookey Michael J.||Remote services system service module interface|
|US20040010575 *||27 Jun 2002||15 Ene 2004||Wookey Michael J.||Remote services system relocatable mid level manager|
|US20040025099 *||31 Jul 2002||5 Feb 2004||Aikawa Susan M.||Method and system for optimizing polling in systems using negative acknowledgement protocols|
|US20040100964 *||27 Nov 2002||27 May 2004||Robotham Robert E.||System and method for detecting lost messages transmitted between modules in a communication device|
|US20040190540 *||22 Dic 2003||30 Sep 2004||Motoharu Miyake||Transmission control method and system|
|US20050021622 *||6 Feb 2004||27 Ene 2005||William Cullen||Dynamic subscription and message routing on a topic between publishing nodes and subscribing nodes|
|US20060069775 *||17 Jun 2004||30 Mar 2006||Artobello Michael R||Apparatus, system, and method for automatically freeing a server resource locked awaiting a failed acknowledgement from a client|
|US20060136580 *||4 Feb 2004||22 Jun 2006||Koninklijke Philips Elecronics N.V.||Method of monitoring the communication in a network|
|US20060271709 *||3 Ago 2006||30 Nov 2006||Rockwell Automation Technologies, Inc.||Bridge for an industrial control system using data manipulation techniques|
|US20070027821 *||11 Jul 2006||1 Feb 2007||Mitsubishi Denki Kabushiki Kaisha||Method for controlling the delivery of a flow of items to at least a client of an item provider|
|US20070106804 *||10 Nov 2005||10 May 2007||Iona Technologies Inc.||Method and system for using message stamps for efficient data exchange|
|US20080065151 *||8 Nov 2007||13 Mar 2008||Ginn Richard S||Locator and delivery device and method of use|
|US20080263424 *||2 Jul 2008||23 Oct 2008||Nokia Corporation||Controlled data network error recovery|
|US20090117924 *||7 Nov 2007||7 May 2009||Motorola, Inc.||System and method for adaptive message retransmission|
|US20100293427 *||15 Jun 2007||18 Nov 2010||Ntt Docomo, Inc.||Radio communications apparatus and method used in a mobile communications system|
|US20120151113 *||14 Jun 2012||Martin Vorbach||Bus systems and methods for controlling data flow in a field of processing elements|
|US20130070686 *||5 Jun 2008||21 Mar 2013||Yan Qun Le||Receiving Unit in a Wireless Communication Network and Method for Generating an Automatic Repeat Request Feedback Message|
|US20130138228 *||16 Nov 2012||30 May 2013||Lsis Co., Ltd.||Motor starter having communication module and control method of motor starter|
|US20130318223 *||25 May 2012||28 Nov 2013||Pro Design Electronic Gmbh||Communication system and communicaton method|
|US20140023083 *||16 Jul 2013||23 Ene 2014||Sensinode Oy||Method and apparatus for exchanging messages|
|USRE44365||21 Oct 2010||9 Jul 2013||Martin Vorbach||Method of self-synchronization of configurable elements of a programmable module|
|USRE45109||21 Oct 2010||2 Sep 2014||Pact Xpp Technologies Ag||Method of self-synchronization of configurable elements of a programmable module|
|USRE45223||21 Oct 2010||28 Oct 2014||Pact Xpp Technologies Ag||Method of self-synchronization of configurable elements of a programmable module|
|CN100407615C||30 Jul 1999||30 Jul 2008||英特尔公司||在网络中发送数据的方法和设备|
|EP0851685A2 *||28 Nov 1997||1 Jul 1998||Oki Electric Industry Co., Ltd.||Video coder, decoder and transmission system|
|EP1071239A1 *||19 Jul 2000||24 Ene 2001||Alstom||Automatic repeat request protocol for radio data communications|
|EP1191733A1 *||1 Nov 1994||27 Mar 2002||Telefonaktiebolaget Lm Ericsson||Automatic retransmission request (ARQ) mode transaction, where a base station determines the status of frames sent to a mobile station|
|EP1424799A2 *||24 Nov 2003||2 Jun 2004||Alcatel Canada Inc.||System and method for detecting lost messages transmitted between modules in a communication device|
|EP1753197A1 *||27 Jul 2005||14 Feb 2007||Mitsubishi Electric Information Technology Centre Europe B.V.||Method for controlling the delivery of a flow of data to at least a client of a data provider|
|WO1995004421A1 *||27 Jun 1994||9 Feb 1995||Motorola Inc||Packet delivery system|
|WO1996021979A1 *||6 Ene 1996||18 Jul 1996||Nicom Ges Fuer Kommunikationss||Process for transmitting data between a transmitter and a receiver in a data network|
|WO1997013379A1 *||29 Ago 1996||10 Abr 1997||Motorola Inc||Reliable wireless message distribution system|
|WO1999017488A1 *||26 Jun 1998||8 Abr 1999||Motorola Inc||Method and apparatus for tracking data packets in a packet data communication system|
|WO1999017489A1 *||12 Jun 1998||8 Abr 1999||Motorola Inc||Method and apparatus for conveying data packets in a packet data communication system|
|WO2001003359A1 *||3 Jul 2000||11 Ene 2001||Nokia Networks Oy||Method and system for data reception acknowledgement|
|WO2001067666A1 *||1 Mar 2001||13 Sep 2001||Ericsson Telefon Ab L M||Efficient header compression context update in packet communications|
|WO2002043403A2 *||20 Nov 2001||30 May 2002||At & T Wireless Services Inc||Enhanced data link layer selective reject mechanism in noisy wireless environment|
|WO2007005114A1 *||10 May 2006||11 Ene 2007||Radioshack Corp||Apparatus for synchronization of digital multimedia data communicated over wired media|
|Clasificación de EE.UU.||714/748, 375/E07.016, 370/450, 370/448, 370/394|
|Clasificación internacional||H04N7/24, H04L1/16, H04L1/18|
|Clasificación cooperativa||H04L1/188, H04L1/1809, H04N21/6377, H04N21/658, H04L1/1607|
|Clasificación europea||H04N21/658, H04N21/6377, H04L1/16F, H04L1/18C, H04L1/18T5|
|10 Mar 1997||FPAY||Fee payment|
Year of fee payment: 4
|10 Nov 1997||AS||Assignment|
Owner name: FISHER-ROSEMOUNT SYSTEMS, INC., A DELAWARE CORPORA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ROSEMOUNT INC.;REEL/FRAME:008811/0675
Effective date: 19970904
|22 Feb 2001||FPAY||Fee payment|
Year of fee payment: 8
|17 Feb 2005||FPAY||Fee payment|
Year of fee payment: 12